1. Field of the Invention
The invention relates to an image processing apparatus and method and, more particularly, to an image processing of image data picked up by an X-ray image pickup apparatus.
2. Related Background Art
In an ordinary X-ray image pickup apparatus, an X-ray beam is irradiated to an object (such as specimen) to be examined such as a medical patient from an X-ray source, for example, in an II (Image Intensifier)-TV system. An X-ray image obtained by the X-ray beam transmitted through the object is converted into a visible light image by an image multiplier or the like, and the visible light image is converted into a video signal by an ordinary video camera or the like. A corresponding video image is displayed on a monitor. At present, an image of a high resolution of (1000.times.1000) pixels or more can be displayed at a rate of 30 frames per second. A technique for converting a video signal into a digital signal in the II-TV system has already been put into practical use.
A solid-state X-ray image sensor of a high resolution has already been proposed. Such a sensor has a 2-dimensional array structure in which 3000 to 4000 detecting devices (for example, photodiodes) are arranged in the respective horizontal and vertical directions. Each detecting device forms an electric signal corresponding to a pixel luminance of an incident X-ray image. The electric signals of the detecting devices are individually read out and converted into digital signals. After that, the digital signals are image processed, stored, and displayed.
In such an image sensor of a high resolution, it is very difficult to fetch all of the pixel signals as moving images and to display all of the pixel signals from the viewpoint of processing speed. So long as only a still image can be derived at an inherent resolution, it cannot be said that a capability of the image sensor is sufficiently brought out.
Although the problem of the processing speed can be solved and a moving image display can be realized by sampling only partial pixels, there is a case where the user wants to observe a target portion as a still image of a high resolution. In the conventional apparatus, it takes a long time to switch from the moving image to the still image and it is fairly difficult to operate the apparatus so as to obtain the still image of the target portion while observing the object to be examined.